Wake vortex interaction effects on energy extraction performance of tandem oscillating hydrofoils

Jianan Xu,Hongyu Sun,Songlin Tan 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.9

An energy extracting technology based on tandem oscillating hydrofoils from flow field is presented in this paper. Numerical simulation were performed to optimize the spatial arrangement for tandem oscillating hydrofoils, the position of the downstream hydrofoil relative to the wake vortex shed by the upstream hydrofoil is seen as critical. Optimized position of the two hydrofoils improves the energy extraction performance through positive interactions between the downstream hydrofoil and the wake vortices of the upstream hydrofoil, and the highest energy extraction efficiency reaches 53.8%. The downstream hydrofoil has a slight impact on the energy extraction performance of the upstream hydrofoil, and the contribution from the upstream hydrofoil is usually slightly inferior to the single hydrofoil results. Leading edge vortex (LEV) is formed and shed from the upstream hydrofoil, which is seen as critical in the energy transformation between the fluid and the energy extraction device. For different reduced frequencies, the energy extraction of a single hydrofoil is heavily influenced by the dynamics of vortex forming and shedding. The investigation was also undertaken over a wide range of kinematic parameters, including hydrofoil separation distance and reduced frequency. Results reveal that energy extraction of tandem oscillating hydrofoils shows better performance than a single hydrofoil for optimal reduced frequency and suitable hydrofoil separation distance.

Modeling and testing for continuously adjustable damping shock absorber equipped with proportional solenoid valve

Jianan Xu,Farong Kou,Xinqian Zhang,Guohong Wang 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.8

A vehicle's solenoid valve-actuated shock (SVSA) absorber is of wide interest because of its adjustable damping characteristics. The proportional solenoid valve is a pivotal component for commanding damping force, but the research on its model principle still needs to be improved. Therefore, this research aimed to establish an accurate model of the proportional solenoid valve composed of the pilot valve and relief valve. In the pilot valve, we proposed a valve spool structure using a two-stage combined throttling groove to control flow accurately. Then, the dynamic equation of the spool was established, and it is also considered that the magnetic saturation of soft magnetic materials impacts electromagnetic force. The flow force in the dynamic equation was numerically solved by the CFD method. The flow rate in the relief valve was analyzed from the deformation of the lamination valves and main valve plate through the small deflections thin plate theory. Then, the SVSA bench test was carried out. The results show good agreement between the test and calculation, and the maximum error is within 9 %. It is indicated that the model of the SVSA equipped with the proportional solenoid valve has high accuracy.

Static behavior of stud shear connectors with initial damage in steel-UHPC composite bridges

Qi, Jianan,Tang, Yiqun,Cheng, Zhao,Xu, Rui,Wang, Jingquan Techno-Press 2020 Advances in concrete construction Vol.9 No.4

For steel-concrete girders made composite using shear studs, initial damage on studs induced by weld defect, unexpected overloading, fatigue and others might degrade the service performance and even threaten the structural safety. This paper conducted a numerical study to investigate the static behavior of damaged stud shear connectors that were embedded in ultra high performance concrete (UHPC). Parameters included damage degree and damage location. The material nonlinear behavior was characterized by multi-linear stress-strain relationship and damage plasticity model. The results indicated that the shear strength was not sensitive to the damage degree when the damage occurred at 2/3d (d is the stud diameter) from the stud root. An increased stud area would be engaged in resisting shear force as the distance of damage location from stud root increased and the failure section becomes inclined, resulting in a less reduction in the shear strength and shear stiffness. The reduction factor was proposed to consider the degradation of the shear strength of the damaged stud. The reduction factor can be calculated using two approaches: a linear relationship and a square relationship with the damage degree corresponding to the shear strength dominated by the section area and the nominal diameter of the damaged stud. It was found that the proposed method is preferred to predict the shear strength of a stud with initial damage.

Effect of a Multi-stage Processing Method on the Composite Properties of a Stainless-Steel Surface

Jing Li,Jianan Cao,Lida Pan,Feng Du,Weibing Wang,Chengyu Xu 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.4

In this study, a multi-stage sandblasting and acid-etching processing method is used to prepare a 304 stainless-steel surfacewith a loose structure that has the composite properties of superhydrophobicity, low adhesion, anti-icing ability, self-cleaningbehavior and corrosion resistance. The surface morphology and chemical constituents of this structure are characterizedby scanning electron microscopy and X-ray diffraction, respectively. The results show that the micro-scale roughness anddifferent degrees of porosity in this structure play a key role in its superhydrophobicity.The anti-icing properties and corrosionresistance are characterized by contact-angle measurements and electrochemical workstation analyses, respectively. The results show that superhydrophobicity has positive effects on surface self-cleaning, anti-icing properties and corrosionresistance of 304 stainless-steel.

Prediction Model for unfavorable Outcome in Spontaneous Intracerebral Hemorrhage Based on Machine Learning

Shengli Li,Jianan Zhang,Xiaoqun Hou,Yongyi Wang,Tong Li,Zhiming Xu,Feng Chen,Yong Zhou,Weimin Wang,Mingxing Liu 대한신경외과학회 2024 Journal of Korean neurosurgical society Vol.67 No.1

Objective : The spontaneous intracerebral hemorrhage (ICH) remains a significant cause of mortality and morbidity throughout the world. The purpose of this retrospective study is to develop multiple models for predicting ICH outcomes using machine learning (ML). Methods : Between January 2014 and October 2021, we included ICH patients identified by computed tomography or magnetic resonance imaging and treated with surgery. At the 6-month check-up, outcomes were assessed using the modified Rankin Scale. In this study, four ML models, including Support Vector Machine (SVM), Decision Tree C5.0, Artificial Neural Network, Logistic Regression were used to build ICH prediction models. In order to evaluate the reliability and the ML models, we calculated the area under the receiver operating characteristic curve (AUC), specificity, sensitivity, accuracy, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR). Results : We identified 71 patients who had favorable outcomes and 156 who had unfavorable outcomes. The results showed that the SVM model achieved the best comprehensive prediction efficiency. For the SVM model, the AUC, accuracy, specificity, sensitivity, PLR, NLR, and DOR were 0.91, 0.92, 0.92, 0.93, 11.63, 0.076, and 153.03, respectively. For the SVM model, we found the importance value of time to operating room (TOR) was higher significantly than other variables. Conclusion : The analysis of clinical reliability showed that the SVM model achieved the best comprehensive prediction efficiency and the importance value of TOR was higher significantly than other variables.

Computation and optimization of rack and pinion steering mechanism considering kingpin parameters and tire side slip angle

Xinqian Zhang,Farong Kou,Guohong Wang,Jianan Xu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.1

In this paper, the parameter optimization and error analysis of the rack and pinion steering mechanism are carried out on the basis of considering the influence of kingpin parameters. The steering characteristic equation describing the motion of the steering mechanism is calculated by analyzing the spatial geometrical relationship between the wheel and kingpin and unifying the projection relation between the kingpin and the equivalent steering trapezoid. The ideal Ackermann equation is modified by the Ackermann rate and the kingpin parameters. The modified Ackermann equation is used as the objective function. The segmented fitness function and the evaluation function with weighted factors are designed. A genetic algorithm containing the three functions is used to optimize the parameters of the steering characteristic equation. The error analysis of the numerical example shows that the accuracy of steering trapezoid structure parameters, steering characteristic equation, and Ackermann equation is improved compared with that before optimization.